The present invention relates to a flexible conveyor belt that is flat in shape when at rest ; the belt comprises internal reinforcement embedded in layers of elastomer material, said reinforcement comprising a first sheet of longitudinal cords providing the belt with longitudinal traction strength, a second sheet of transverse cords providing the belt with transverse traction strength, and a stiffening layer having high resistance to transverse compression relative to the resistance to transverse compression of the second sheet.
Document EP-A-0 047 739 describes a belt of this type; the stiffening layer is narrow and received in the central portion of the belt; the width of the layer is substantially equal to the individual length of each roller belonging to a support row for the central portion of the belt in a conveyor. Belts of that structure can be used for transporting bulk materials in conveyors that have a plurality of parallel rows of rollers imparting the shape of a flat-bottomed trough to the belt.